JP2008176045A - Camera system, lens assembly and camera body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a camera system or the like capable of preventing the rear end part of a lens barrel from interfering with the internal parts of a camera when mounting a lens having a short back focus in a camera body. <P>SOLUTION: In the camera system 1, the camera body 2 and the lens assembly 4 having a second back focus shorter than a first back focus equivalent to the flange back of the camera body 2 are constituted to be attachable/detachable through engaging sections 20 and 21. The lens assembly 4 has a lens barrel 27 which can be elongated to an image side, and is set to the second back focus in such a state that the lens barrel 27 is elongated to the image side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a camera system, a lens structure, and a camera body.

2. Description of the Related Art Conventionally, there has been proposed a camera having a configuration in which a lens having a different image circle can be attached and an image acquisition range of the image sensor is changed according to the size of the image circle of the attached lens (for example, Patent Document 1). See).
JP 2005-176147 A

  Here, in the conventional camera as described above, as a lens having a small image circle, it is advantageous in design to shorten the back focus of the lens. However, if the back focus of the lens is shortened, the rear end portion of the lens barrel interferes with internal parts of the camera (for example, a quick return mirror of a single-lens reflex camera) when the lens is mounted on the camera body. There was a problem.

  Accordingly, the present invention has been made in view of the above problems, and a camera system that prevents the rear end portion of the lens barrel from interfering with internal components of the camera when a lens with a short back focus is attached to the camera body. An object is to provide a lens structure and a camera body.

In order to solve the above problems, the present invention
A camera system in which a camera body and a lens structure having a second back focus shorter than a first back focus corresponding to a flange back of the camera body are configured to be detachable via an engaging portion,
The lens structure includes a lens barrel that can be extended to the image side, and the second back focus is set in a state where the lens barrel is extended to the image side.

The present invention also provides
A lens structure having an optical system and configured to be detachable from the camera body,
An engaging portion that engages with the camera body;
Provided is a lens structure having a lens barrel that can be extended toward the image side of the optical system with respect to the engaging portion.

The present invention also provides
A camera body capable of selectively mounting multiple types of lens structures with different back focus,
Imaging means;
Detecting means for detecting information relating to the back focus of the lens structure;
There is provided a camera body comprising control means for changing an image acquisition range in the imaging means based on information detected by the detection means.

  According to the present invention, there are provided a camera system, a lens structure, and a camera body that prevent a rear end portion of a lens barrel from interfering with an internal part of the camera when a lens with a short back focus is attached to the camera body. be able to.

Hereinafter, a camera system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram (using an extension type interchangeable lens) showing a configuration of a camera system according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram showing a state in which a normal interchangeable lens is used in the camera system according to the embodiment of the present invention.
FIG. 3 is a schematic configuration diagram showing a state in which an interchangeable lens having a short back focus (referred to as a small Bf interchangeable lens) is used in the camera system according to the embodiment of the present invention.

As shown in the drawings, the camera system 1 is provided with an interchangeable lens mounted on a camera body 2, and the camera body 2 includes an ordinary interchangeable lens 3 as an interchangeable lens, an extension interchangeable lens 4 described later, In addition, it is possible to selectively mount a small Bf interchangeable lens 5 described later.
First, the overall configuration of the camera system 1 will be described with reference to FIG. 2 showing a state where a normal interchangeable lens 3 is attached. The normal interchangeable lens 3 generally refers to an interchangeable lens having a back focus longer than the flange back of the camera body 2.

  An ordinary interchangeable lens 3 includes an optical system 6 that collects light from a subject (not shown), a lens driving device 7 that drives the optical system 6 in the optical axis direction, and a lens control circuit that controls the lens driving device 7. 8 is provided. The lens control circuit 8 has information such as the type of interchangeable lens, back focus, and image circle.

The camera body 2 includes a main mirror 9 that reflects light from the subject collected by the interchangeable lens 3 upward, a focusing plate 10 and a pentaprism 11 that are disposed on a reflection light path of the main mirror 9, and the pentaprism. 11 has an eyepiece 12 arranged on the exit surface side, and further, a sub-mirror 13, a shutter 14, and an image sensor 15 are provided behind the main mirror 9. The camera body 2 includes a focus detection element 16 on the reflected light path of the sub mirror 13, a photometric optical system 17 near the exit surface of the pentaprism 11, a camera control circuit 18 below the camera body 2, and a display element 19 on the back of the camera body 2. have.
The main mirror 9 and the sub mirror 13 can be lifted up to the focusing screen 10 side and retracted out of the optical path as shown in FIGS. 1B and 3 by a known flip-up mechanism (not shown). In addition, a mirror up button (not shown) is provided outside the camera body 2 so that the photographer can arbitrarily operate the main mirror 9 and the sub mirror 13 to be retracted from the optical path.

  The interchangeable lens 3 is attached to the camera body 2 having such a configuration by engaging bayonet mounts 20 and 21 provided on the camera body 2 and the interchangeable lens 3, respectively. Further, camera-side communication contacts 22 and lens-side communication contacts 23 are provided at the ends of the mounts 20 and 21, respectively. When the interchangeable lens 3 is attached to the camera body 2, these contacts are connected. Through this, the lens control circuit 8 and the camera control circuit 18 can communicate with each other.

  In the camera system 1 configured as described above, light from a subject (not shown) is collected by the optical system 6 of the interchangeable lens 3, reflected upward by the main mirror 9 in the camera body 2, and connected to the focusing screen 10. Imaged. The light imaged on the focusing screen 10 is reflected by the pentaprism 11 and can be observed by the photographer via the eyepiece 12. As a result, the photographer can confirm the subject image as an erect image.

The central portion of the main mirror 9 is a half mirror surface, and light transmitted through this portion is reflected by the sub mirror 13 and guided to the focus detection element 16. Thus, the camera control circuit 18 calculates the focusing movement amount of the optical system 6 based on the output of the focus detection element 16 and controls the lens driving device 7 via the lens control circuit 8 to drive the optical system 6. Focusing can be performed.
The photometric optical system 17 provided in the vicinity of the exit surface of the pentaprism 11 measures the diffused light of the focusing screen 10, so that the camera control circuit 18 takes an image based on the output from the photometric optical system 17. The exposure time can be determined.

  Further, when a release button (not shown) provided outside the camera body 2 is operated by the photographer, the main mirror 9 and the sub mirror 13 are flipped upward and retracted out of the optical path, and the shutter 14 is opened. Light from the subject reaches the image sensor 15. Thereby, the light from the subject is picked up by the image pickup device 15, displayed on the display device 19, and recorded as a subject image in a memory (not shown). In this way, the photographer can photograph the subject using the normal interchangeable lens 3 in the camera system 1.

  As shown in FIG. 4A, the normal interchangeable lens 3 having a back focus Bf.1 longer than the flange back f.b. of the camera body 2 has an image circle 25 having a diameter φ1. For this reason, the image pickup device 15 acquires an image in the range of the shooting screen in accordance with the image circle 25, that is, the rectangular range having a predetermined aspect ratio in the image circle 25 (all shooting screens 26). Here, the back focus means a distance from the lens surface closest to the image side in the optical system 6 of the interchangeable lens to the image sensor 15, and the flange back means from the reference surface of the mount 20 of the camera body 2 to the image sensor 15. The distance.

Next, in the present camera system 1, a case where an interchangeable lens (hereinafter referred to as “expandable interchangeable lens”) having a lens barrel that can be expanded toward the image side is mounted on the camera body 2 will be described with reference to FIG. 1. explain.
As shown in FIG. 1, the extension type interchangeable lens 4 includes a lens barrel 27 that can be extended to the image side from the mount 21 by a known feeding / collapse mechanism. Thus, the extension type interchangeable lens 4 is moved from the retracted state in which the lens barrel 27 is retracted to a use state in which the lens barrel 27 is extended and the rear end of the lens barrel 27 is arranged on the image side from the mount 21. The form can be changed. Therefore, the extension type interchangeable lens 4 does not interfere with the configuration of the mirror 9 and the like of the camera body 2 in the retracted state, and is shorter than the first back focus in the used state as shown in FIG. 4B. 2 back focus Bf. It is comprised so that it may become two.

Further, when the extension type interchangeable lens 4 is mounted on the camera body 2, the lens barrel fixing pin 28 protrudes from the end of the mount 21 and is inserted into the camera body 2. The lens barrel fixing mechanism 29 that fixes the extension type interchangeable lens 4 and the camera body 2 is provided.
In addition, since the other structure in this expansion | extension type interchangeable lens 4 is the same as that of the structure of the normal interchangeable lens 3 mentioned above, the same number is attached | subjected and description is abbreviate | omitted.

  When the extension type interchangeable lens 4 having such a configuration is attached to the camera body 2, the lens barrel 27 is prevented from colliding with the main mirror 9 in the camera body 2, so that the lens barrel 27 is retracted as shown in FIG. 1, and after retracting the main mirror 9 and the sub mirror 13 to the outside of the optical path, the lens barrel 27 is extended and put into use as shown in FIG. Details of this procedure will be described later.

When the extension type interchangeable lens 4 having the above configuration is used in the camera system 1, light from a subject (not shown) is collected by the extension type interchangeable lens 4, passes through the opened shutter 14, and the image sensor 15. To reach. Thereby, the light from the subject is picked up by the image pickup device 15, displayed on the display device 19, and recorded as a subject image in a memory (not shown). In this way, the photographer can take an image of the subject using the extension type interchangeable lens 4 in the camera system 1.
When the extension type interchangeable lens 4 is used in the camera system 1, the main mirror 9 is retracted from the optical path as described above, so that the focusing plate 10, the pentaprism 11, and the eyepiece 12 are used. The optical finder can not be used. However, it is possible to replace the optical viewfinder by displaying an image obtained by the imaging element 15 on the display element 19 during photographing.

  Further, as shown in FIG. 4B, the extension type interchangeable lens 4 having a back focus Bf.2 shorter than the flange back f.b. of the camera body 2 in the use state is the same as the normal interchangeable lens 3 described above. An image circle 30 having a diameter φ2 smaller than the image circle 25 is formed on the image sensor 15. For this reason, in the image pickup device 15, the image acquisition range on the shooting screen is changed according to the image circle 30, and an image is acquired in a rectangular range (shooting screen 31) with a predetermined aspect ratio in the image circle 30. It becomes. Thereby, the camera system 1 can capture a good image without vignetting. The image acquisition range is changed by the camera control circuit 18 of the camera body 2 based on back focus information and image circle information of the interchangeable lens obtained from the lens control circuit 8 as described later.

Next, in the camera system 1, FIG. 3 shows a case where an interchangeable lens (hereinafter referred to as “small Bf interchangeable lens”) having a lens barrel protruding toward the image side from the mount 21 is attached to the camera body 2. The description will be given with reference.
As shown in FIG. 3, the small Bf interchangeable lens 5 includes a lens barrel 32 that protrudes from the mount 21 toward the image side. Therefore, the small Bf interchangeable lens 5 has a back focus of the camera body 2 of the flange back f. b. Shorter than.

  The small Bf interchangeable lens 5 having such a configuration is attached to the camera body 2 in order to prevent the lens barrel 32 from colliding with the main mirror 9 in the camera body 2, so that the main mirror 9 and the sub mirror 13 are previously moved out of the optical path. The procedure is performed by retracting and then attaching the small Bf interchangeable lens 5 to the camera body 2. Details of this procedure will also be described later.

When the small Bf interchangeable lens 5 having the above configuration is used in the camera system 1, light from a subject (not shown) is collected by the small Bf interchangeable lens 5, passes through the opened shutter 14, and the image sensor 15. To reach. Thereby, the light from the subject is picked up by the image pickup device 15, displayed on the display device 19, and recorded as a subject image in a memory (not shown). In this way, the photographer can photograph the subject using the small Bf interchangeable lens 5 in the camera system 1.
When the small Bf interchangeable lens 5 is used in the camera system 1 as described above, the optical viewfinder is used because the main mirror 9 is retracted out of the optical path as in the case of the extendable interchangeable lens 4. It is not possible. However, it is possible to replace the optical viewfinder by displaying an image obtained by the imaging element 15 on the display element 19 during photographing.

  The small Bf interchangeable lens 5 has a back focus of the camera body 2 as described above. b. Therefore, an image circle having a smaller diameter than the image circle 25 of the above-described normal interchangeable lens 3 is formed on the image sensor 15. For this reason, in the image pickup device 15, as in the extension type interchangeable lens 4, the image acquisition range is changed according to the image circle, and a good image without vignetting is taken.

  With the above configuration, in the camera system 1, when the extension type interchangeable lens 4 or the normal interchangeable lens 3 is mounted on the camera body 2, the first interchangeable lens mounting routine described below is executed. When the Bf interchangeable lens 5 or the regular interchangeable lens 3 is mounted on the camera body 2, the photographer operates a mirror up button (not shown) and then a second interchangeable lens mounting routine described later is executed. Hereinafter, these interchangeable lens mounting routines will be described with reference to the accompanying drawings.

The first interchangeable lens mounting routine shown in FIG. 5 is performed when the photographer attaches the expandable interchangeable lens 4 or the normal interchangeable lens 3 to the camera body 2 and turns on the camera body 2, or This process is started when the extension type interchangeable lens 4 or the normal interchangeable lens 3 is attached to the camera body 2 in a state where is inserted.
Step S1: The camera control circuit 18 of the camera body 2 obtains back focus information from the lens control circuit 8 of the mounted interchangeable lens, and this back focus is converted to the flange back f. b. It is determined whether or not the following is true (whether the attached interchangeable lens is the expansion interchangeable lens 4 or the normal interchangeable lens 3). Back focus is flange back f. b. If it is the following (in the case of the extension type interchangeable lens 4), the process proceeds to step S2. If not (in the case of the normal interchangeable lens 3), the first interchangeable lens mounting routine is ended.

Step S2: The camera control circuit 18 controls the lens barrel fixing mechanism 29 via the lens control circuit 8 so that the lens barrel fixing pin 28 protrudes from the mount 21 and is inserted into the camera body 2, whereby the extendable interchangeable lens 4. Is fixed to the camera body 2.
Step S3: The camera control circuit 18 raises the main mirror 9 and the sub mirror 13 and retracts them out of the optical path.
Step S <b> 4: The camera control circuit 18 outputs an extension permission signal for the lens barrel 27 to the lens control circuit 8. As a result, the lens control circuit 8 extends the lens barrel 27 to the image side, and the extension type interchangeable lens 4 is put into use.

Step S5: The camera control circuit 18 opens the shutter 14.
Step S6: The camera control circuit 18 obtains image circle information and the like from the lens control circuit 8.
Step S7: The camera control circuit 18 determines an image acquisition range on the imaging screen of the imaging device 15 based on the image circle information obtained in step S6.
Step S <b> 8: When the photographer shoots a subject using the camera system 1, the camera control circuit 18 displays the photographed image on the display element 19. This completes the first interchangeable lens mounting routine.

  The camera system 1 executes the first interchangeable lens mounting routine described above, so that the rear end portion of the lens barrel 27 does not interfere with the internal components in the camera body 2 such as the main mirror 9 and the extension type replacement is possible. The lens 4 can be attached to the camera body 2.

In the second interchangeable lens mounting routine shown in FIG. 6, the small Bf interchangeable lens 5 or the normal interchangeable lens 3 is mounted on the camera body 2 after the photographer operates the mirror up button (not shown) as described above. Will be started.
Step P1: The camera control circuit 18 of the camera body 2 obtains back focus information from the lens control circuit 18 of the mounted interchangeable lens, and this back focus is converted to the flange back f. b. It is determined whether or not the following is true (whether the attached interchangeable lens is the small Bf interchangeable lens 5 or the normal interchangeable lens 3). If the back focus is less than the flange back (in the case of the small Bf interchangeable lens 5), the process proceeds to Step P2, and if not (in the case of the normal interchangeable lens 3), the process proceeds to Step P6.

Step P2: The camera control circuit 18 opens the shutter 14.
Step P3: The camera control circuit 18 obtains image circle information and the like from the lens control circuit 8.
Step P4: The camera control circuit 18 determines an image acquisition range on the imaging screen of the imaging device 15 based on the image circle information obtained in Step P3.
Step P5: When a subject is photographed by the photographer using the camera system 1, the camera control circuit 18 displays the photographed image on the display element 19. This completes the second interchangeable lens mounting routine.

Step P6: The camera control circuit 18 returns the main mirror 9 and the sub mirror 13 that have been retracted out of the optical path to the optical path, and the second interchangeable lens mounting routine ends.
The camera system 1 executes the second interchangeable lens mounting routine described above, so that the rear end portion of the lens barrel 32 does not interfere with internal components in the camera body 2 such as a main mirror, and the small Bf interchangeable lens. 5 can be attached to the camera body 2.

  In the camera system 1, when the interchangeable lens attached to the camera body 2 is removed, first, second, and third interchangeable lens removal routines described below are executed. Note that these interchangeable lens removal routines are executed corresponding to the interchangeable lens mounted on the camera body 2, and more specifically, the first interchangeable lens when the expansion-type interchangeable lens 4 is mounted. When the small Bf interchangeable lens 5 is attached, the second interchangeable lens removal routine is executed. When the normal interchangeable lens 3 is attached, the third interchangeable lens removal routine is executed. Is executed. Hereinafter, these interchangeable lens removal routines will be described with reference to the accompanying drawings.

In the first interchangeable lens removal routine shown in FIG. 7, when the extendable interchangeable lens 4 is mounted on the camera body 2, a photographer operates a lens attaching / detaching button (not shown) provided on the camera body 2. It starts with that.
Step T1: The camera control circuit 18 closes the shutter 14.
Step T2: The camera control circuit 18 outputs a storage command signal for the lens barrel 27 to the lens control circuit 8. Thereby, the lens control circuit 8 retracts and stores the lens barrel 27, and the extension type interchangeable lens 4 enters a retracted state.

Step T3: The camera control circuit 18 returns the main mirror 9 and the sub mirror 13 that have been retracted out of the optical path to the optical path.
Step T4: The camera control circuit 18 controls the lens barrel fixing mechanism 29 via the lens control circuit 8 to retract the lens barrel fixing pin 28 from the camera body 2, thereby fixing the extension type interchangeable lens 4 and the camera body 2. Is released. As a result, the photographer can remove the extendable interchangeable lens 4 from the camera body 2, and the first interchangeable lens removal routine is completed.

  The camera system 1 executes the first interchangeable lens removal routine described above, so that the rear end portion of the lens barrel 27 does not interfere with internal parts in the camera body 2 such as the main mirror 9, and the extension type exchange is possible. The lens 4 can be removed from the camera body 2.

The second interchangeable lens removal routine shown in FIG. 8 is started when the photographer operates a lens attachment / detachment button (not shown) when the small Bf interchangeable lens 5 is attached to the camera body 2.
Step Q1: The camera control circuit 18 closes the shutter 14. As a result, the photographer can remove the small Bf interchangeable lens 5 from the camera body 2.
Step Q2: After the small Bf interchangeable lens 5 is removed from the camera body 2 by the photographer, the camera control circuit 18 returns the main mirror 9 and the sub mirror 13 that have been retracted out of the optical path to the optical path. This completes the second interchangeable lens removal routine.

  The camera system 1 executes the above-described second interchangeable lens removal routine, so that the small Bf is exchanged without causing the rear end portion of the lens barrel 32 to interfere with internal parts in the camera body 2 such as the main mirror 9. The lens 5 can be removed from the camera body 2.

  In the camera system 1, when each interchangeable lens is attached to and detached from the camera body 2, the camera control circuit 18 in the camera body 2 supplies power to the camera side communication contact 22 and the lens side communication contact 23 of each interchangeable lens. It is done by detecting. However, this detection may be performed by separately arranging the attachment detection means and the removal detection means in the camera body 2.

  As described above, the camera system 1 performs the flange back f.f of the camera body 2 by executing the above-described interchangeable lens mounting routine and each interchangeable lens removal routine. b. Use the extension type interchangeable lens 4 and the small Bf interchangeable lens 5 having a larger back focus by selectively attaching the rear end portion of the lens barrel to the camera body 2 without causing interference with the internal parts of the camera. Can do.

  Therefore, in this camera system 1, since it is possible to use an interchangeable lens having different back focus at the same time as the image circle, the degree of freedom in lens design is improved, and it is possible to use interchangeable lenses having various characteristics. For example, when trying to realize an interchangeable lens with the same angle of view as in full-screen shooting with a shorter focal length, it is very difficult to design an interchangeable lens with a small focal length while maintaining the back focus. Therefore, it is a great merit that the back focus can be reduced in proportion to the focal length. Further, if interchangeable lenses having the same angle of view and different focal lengths are used, it is possible to shoot with different depths of field while maintaining the same angle of view and F value, and the degree of freedom of shooting is greatly improved. For example, if the extension type interchangeable lens 4 or the small Bf interchangeable lens 5 is used, a large depth of field can be ensured and a moving image can be taken without a focus shift.

  Further, the present camera system 1 has a configuration in which the shutter 14 is opened after the interchangeable lens is mounted and the shutter 14 is closed in advance when the interchangeable lens is removed by each interchangeable lens mounting routine and each interchangeable lens removal routine. It is possible to prevent dust and dirt from entering and adhering to the image sensor 15.

1 is a schematic configuration diagram (using an extension type interchangeable lens) showing a configuration of a camera system according to an embodiment of the present invention. It is a schematic block diagram which shows a mode that the normal interchangeable lens is used in the camera system which concerns on embodiment of this invention. It is a schematic block diagram which shows a mode that the small Bf interchangeable lens is used in the camera system which concerns on embodiment of this invention. It is a flowchart which shows the 1st interchangeable lens mounting routine in the camera system which concerns on embodiment of this invention. It is a flowchart which shows the 2nd interchangeable lens mounting routine in the camera system which concerns on embodiment of this invention. It is a flowchart which shows the 3rd interchangeable lens mounting routine in the camera system which concerns on embodiment of this invention. It is a flowchart which shows the 1st interchangeable lens removal routine in the camera system which concerns on embodiment of this invention. It is a flowchart which shows the 2nd interchangeable lens removal routine in the camera system which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera system 2 Camera body 3 Normal interchangeable lens 4 Extendable interchangeable lens 5 Small Bf interchangeable lens 6 Optical system 8 Lens control circuit 18 Camera control circuit 27, 32 Lens barrel

Claims (9)

A camera system in which a camera body and a lens structure having a second back focus shorter than a first back focus corresponding to a flange back of the camera body are configured to be detachable via an engaging portion,
2. The camera system according to claim 1, wherein the lens structure includes a lens barrel that can extend toward the image side, and the second back focus is set in a state where the lens barrel extends toward the image side.   The camera system according to claim 1, wherein the camera body includes an optical path switching unit provided so as to be able to advance and retract in an optical path from the lens structure. The camera body includes detection means for detecting attachment of the lens structure;
And a control unit that allows the lens barrel to extend to the image side in a state where the optical path switching unit is retracted out of the optical path when the detection unit detects the mounting of the lens structure. Item 3. The camera system according to Item 2. The camera system according to claim 1,
The camera body has a detachment detecting means for detecting an operation of detaching the lens structure,
A camera system comprising: control means for retracting the lens barrel into the lens structure when the detachment operation of the lens structure is detected by the detachment detection means. The camera system according to claim 2,
The camera body has a detachment detecting means for detecting an operation of detaching the lens structure,
And a control means for allowing the optical path switching means to enter the optical path after the lens barrel is retracted into the lens structure when the separation detecting means detects the lens body separation operation. A featured camera system. A lens structure having an optical system and configured to be detachable from the camera body,
An engaging portion that engages with the camera body;
A lens structure having a lens barrel that can extend toward the image side of the optical system with respect to the engaging portion. A camera body capable of selectively mounting multiple types of lens structures with different back focus,
Imaging means;
Detecting means for detecting information relating to the back focus of the lens structure;
A camera body comprising: control means for changing an image acquisition range in the imaging means based on information detected by the detection means. A camera body according to claim 7,
An optical path switching means provided so as to be able to advance and retreat in the optical path of the light beam from the lens structure;
The camera body characterized in that the control means controls the position of the optical path switching means based on information detected by the detection means. An engaging portion capable of mounting a lens structure having a lens barrel that can be extended to the image side of the optical system;
A detection unit for detecting the mounting of the lens structure;
A camera body, comprising: a control unit configured to extend the lens barrel when the detection unit detects that a lens structure having the lens barrel is attached.

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